A/D conversion circuits that convert analog signals to digital signals are known. An A/D conversion circuit in which a ratio between tail currents at a differential pair to which a differential input signal is inputted is made to differ is known (e.g., Japanese Laid-open Patent Publication No. 2003-158456 and Japanese Laid-open Patent Publication No. 2011-29983). An asynchronous reception circuit in which interpolation data is generated by interpolating sampled input data is known (e.g., Japanese Laid-open Patent Publication No. 2012-147079).
For example, when the interpolation data is generated from the sampled input data, the input data is weighted and combined, and thus the interpolation data is generated. A decision is made so as to digitize the interpolation data. The size of a circuit for carrying out the weighting and making the decision increases.